| Temporal changes in biological community structure from the apparent "birth" of numerous deep-sea hydrothermal vents were documented following the April 1991 discovery of newly-formed vents on the East Pacific Rise. Photo- and videographic documentation of megafaunal colonization and chemical analyses of diffuse hydrothermal fluids associated with these developing communities were conducted over a 4.5 year period within an on-bottom observatory, the Biologic-Geologic Transect, between 9;The evolutionary history and systematic relationships of shrimp (Caridea: Bresiliidae) inhabiting deep-sea hydrothermal vent and hydrocarbon seep environments was assessed using the mitochondrial Cytochrome c Oxidase subunit I (COI) gene. Phylogenetic analyses recovered three distinct clades (A, Rimicaris/Chorocaris/Opaepele, B, Alvinocaris, and C, Mirocaris) consistent with morphologically-based taxonomy. However, the genus Chorocaris is paraphyletic and Mirocaris fortunata and M. keldyshi may not be genetically distinct. Independent species descriptions of a "small orange" caridean shrimp found at deep-sea hydrothermal vents along the Mid-Atlantic Ridge created the synonymous names, Iorania concordia Vereshchaka (1996b) and Rimicaris aurantiaca Martin et al. (1997). Genetic analyses involving allozymes and mitochondrial DNA sequences reveal that the "small orange" shrimp are actually a juvenile form of Rimicaris exoculata Williams and Rona (1986). Evolutionary relationships of vent-endemic shrimp species are not correlated to their extant biogeographic distributions or history of sea-floor spreading. Additionally, COI data suggest these vent-endemic organisms are not remnants of a Mesozoic vent assemblage. Molecular estimates of divergence suggest bresiliids radiated not more than 20 MYA during the Miocene, and comprise the youngest vent and seep-associated diversification. |
